This invention is related to an X-ray apparatus for diagnosis of patients.
An X-ray apparatus has an X-ray limiting device, adjusting an X-ray irradiation field, attached to an aperture, for irradiating X-rays, of an X-ray tube. This X-ray limiting device makes it possible to reduce X-ray exposure dose of a person and also to enhance an X-ray image.
In this X-ray apparatus, an X-ray limiting device 4 is attached to an aperture, for irradiating X-rays, of an X-ray tube 3 which is held to a supporting arm 35, as shown in FIG. 7. An image intensifier 5 is attached below the table 1 upon which rests a person 2 for examination. The whole structures, including the supporting arm 35, the image intensifier 5, and so on, are supported by a supporting base 36.
As shown in FIG. 7, the X-ray limiting device 4 has two stages of blades which consist of lower blades 7, 8 and upper blades 9, 10. The lower blades 7 and 8 limit X-rays in the right and left directions, facing the FIG. 7. The upper blades 9 and 10 limit X-rays in the front and back directions, facing the FIG. 7. X-rays generated at an X-ray focal point 3a are limited by these blades 7, 8, 9, and 10 to form an X-ray flux 19 and then are irradiated onto the target part of the person 2.
When imaging the left part of the person 2, the table 1 is moved in the direction shown as the arrow A until the center of the imaging part of the image intensifier 5 and the center of an X-ray irradiation field reach the target part of the left part, and then imaging of the target part is carried out. When imaging the right part of the person 2, the table 1 is moved in the direction along the arrow B until the center of the imaging part of the image intensifier 5 and the center of an X-ray irradiation field reach the target part of the left part, and then imaging of the target part is carried out.
The following is a description of a structure of the X-ray limiting device 4, with reference of FIG. 8. The lower blades 7, 8, formed mainly of laden boards, are disposed in a case 25 and limit X-ray flux 19 to form a necessary and sufficient X-ray irradiation field. The lower blades 7, 8 are driven in a circular movement by a gear and link structure, or in a parallel movement by wire ropes, pulleys, and shafts disposed in parallel. The former allows for a simple structure. The other one makes it possible to limit an X-ray irradiation field accurately.
The upper blades 9, 10 and back blades (not illustrated) are also driven, engaging with the lower blades 7, 8. A small motor can be used to drive these blades. The upper blades 9, 10 greatly contribute to reduction of scattered radiation and leakage dose. The back blades efficiently reduce X-rays generated from the part other than the focal point 3a. The total performance of these three pairs of blades depends on their assembly dimensional accuracy and geometric relation to one another, as well as the performance of each blade.
The X-ray irradiation field is confirmed in a manner of visual observation of an optical irradiation field shown on the person 2. The optical irradiation field is formed by light, from a projector 13, reflecting on the mirrors 14, 15 and then going by the lower blades 7, 8. The X-ray irradiation field is also confirmed in a manner of visual observation of a needle 16 which moves, along a scale board 17, engaging with the lower blades 7, 8. These indicators make it possible to confirm the X-ray irradiation field without irradiating X-rays actually. Some of the prior art X-ray limiting devices do not have projector 13. A detachable filter 18 for controlling an amount of the total leakage which regulates X-ray quality is also usually provided with the X-ray limiting device 4.
In the conventional X-ray apparatus, constructed as described above, an imaging part which has the X-ray tube 3, the image intensifier 5, a snap shot device, not shown in the Figures, and so on, is fixed not to move along the width of the person 2, through the supporting arm 35. Thus, it is necessary to move the table 1 for changing an imaging area along the width of the person 2. When an examination with a brouchoscope, endoscope, and so on is also carried out, with the hardware inserted into the person being examined, this results in a heavy burden on the person 2. Also when an examination, making an X-ray irradiation field smaller with the X-ray limiting device 4 than the field of view of the image intensifier 5 for the purpose of reducing useless exposure, is carried out, the same problem occurs when changing an imaging area along the width of the person 2.
It is, therefore, an object of this invention to provide an X-ray apparatus which makes it possible to change an imaging area along the width of the person 2, for example, without burdening the person 2 in an examination with a brouchoscope, endoscope, and so on.
An X-ray apparatus of this invention has an X-ray tube, a solid state flat detector opposing said X-ray tube across a person for examination, an X-ray limiting device for limiting the X-rays from said X-ray tube, and a driver for rotating said X-ray tube and said X-ray limiting device along a plane which is perpendicular to the body axis of the person.
The X-ray apparatus also has an edge detector for detecting X-ray irradiated onto an edge part of the solid state flat detector, a controller for receiving a signal from the edge detector and controlling, with the signal, the X-ray limiting device so that X-rays do not come outside of the solid state flat detector.
In the X-ray apparatus, the edge detector consists of X-ray semiconductor elements in edge parts on the solid state flat detector.
In the X-ray apparatus, the edge detector may also consist of a separate X-ray detector from the solid state flat detector.
The X-ray apparatus also has a handle for providing signals depending on an amount set by an operator, and an X-ray tube rotation controller for rotating the X-ray tube depending on the signals.
The X-ray apparatus also has two handles for providing signals based on amounts set by an operator, and a shield blade movement controller for moving the two shield blades independently, depending on the signals.
The X-ray apparatus also has a detector for detecting a rotation angle of the X-ray tube, and providing signals related to the rotation angle, a controller for receiving the signals from the detector and controlling the X-ray limiting device so that X-rays from the X-ray tube do not go outside of the solid state flat detector.